THE CLUTCH.

Greymouth Evening Star, 14 September 1934, Page 4

THE CLUTCH.

NEED FOR CAREFULNESS Whether or clutch acts efficiently for long periods at a time I without attention depends so nau< ; ll i upon its design that it is as well to know what troubles may be expected and how they may best be overcome. Naturally the life of the clutch depends tremendously on the way in. which the car is driven. If. for instance the lazy driver slips the clutch instead of changing down for corners and traffic; if, also he .tries to get away on top gear when he has two or three other speeds to fall back upon, and if he lets it in with a jerk when starting off or changing gear, he must be prepared to give this important component of the chassis a good deal more attention than would otherwise bo necessary. v There is the multiple disc clutch, in which a number of exceedingly thin steel plates are brought into engagement with a similar set spliced to the end of the main shaft. The dry-plate type generally consists of a ring of steel ox* aluminium alloy, faced with abestos composition and connected to the clutch shaft by a spider—-i.e., four’ or five arms of metal radiating fiom its peripliery to a collar on the shaft. One more method of connecting up the engine to the rear wheels must be mentioned, and this is by the contracting band used in epicyclic gears such as the Ford low and reverse gears, and at the other end of the scale, the Lanchester gears. One of the most annoying faults to which clutches are heir is slipping. This usually means that with the wheels on soft ground, or the car on a gradient, the powei’ will not be transmitted from the engine to the wheels; in. bad cases it will prevent a start being made even in the level. Another reason why the clutch slips can sometimes be traced to the fact that the lining is much worn, so that the edge of the metal cone to. which it is attached make contact with the flywheel. Again, uneven wear may cause the surface of the leather to grip only in places not. sufficiently to enable the full power of the engine to be transmitted. Too weak a clutch spring also may be a cause of trouble. A clutch on which there are high spots may be levelled off sometimes, but it often pays to fit a new leather. A weak clutch spring can be remedied by increasing its tension, if means'be provided, otherwise packing behind it one or more washers, and in extreme cases by replacing the spring with a stronger one. A multiple-disc clutch may slip through excess of oil, in which case the old lubricant should be drained out and the clutch flushed with paraffin ; or because it is in need of adjustment, which is usually carried out without much difficulty. No more oil than is recommended by the makers of the clutch should be put The slipping of a single-plate clutch may be due to excess of oil or insufficient spring tension.

PISTON DISTORTION The merits of aluminium pistons are such that they have now generally supplanted the cast-iron type, but one of the disadvantages which had to be overcome was the tendency of an aluminium piston to distort under load (states an English paper). Various means of combating that have been applied successfully, but a new design of piston which has been developed by a renowned British engineering works promises to give exceptionally good results. The inherent inability of an aluminium piston to retain its shape under working conditions arises principally from the uneven expansion of the metal, a factor which is governed largely by the distribution of the mass of the metal in the casting. Furthermore, the skirt of an aluminiumpiston, it is explained, tends to expand because of the deflection of the piston head during the firing stroke, and is prone to assume, speaking in microscopic terms, an oval shape but reverts to normal on the return stroke of the piston. Various methods have been applied to “abolish that characteristic, among them being the practice of machining the piston in such a way that it is not truly cylindrical, but slightly oval in form. The latest system is to join the thrust sides of the piston skirt to the piston crown by two arched struts, which offer resistance to the inward movement of ftie walls of the skirt and so prevent the skirt from losing its shape. A subsidiary function of the struts which are of large size is to help in. the dissipation of the heat, which is carried away more rapidly from the piston crown and the rings. It is claimed that because of these advantages the normal clearance between the piston and the cylinder can be reduced, so that the likelihood of piston slap or over-oiling occurring is minimised.

CHECK THE STEERINGIt is advisable, to give the steering a periodical inspection to prevent costly repairs, and to assure the safety of yourself and the passengers. Excessive play in the steeringshould be checked. Steering drag link and tie rods should be examined for slackness. These should be adjusted regularly, or, if wear is excessive, replacement of ball joints should be effected. Slackness in the steering box should be checked as follows: — End play in steering worm. This can be rectified by adjusting the large nut on the top of the box or removing the shims from the bottom plate. ( To take out end play from the sector shaft, remove the shim from the side plate, or adjust thrust screw if provided. Play between the steering sector and worm can be regulated by adjustment of the steering flange or the eccentric bush on the sector shaft. BRITAIN’S ACCIDENT RATE. Curing the 18 weeks ended July 14 in Britain, there were 2410 people killed and <82,658 injured. During the 16 weeks from March 11 to June 30 London had the worst record, with 425 deaths. Yorkshire camo next with 177. and Lancashire v. ith 165. Rutland had the lowest record, returning only three fatalities, while Dorset recorded five and Cam- 1 bi idgeshire six. Luring this period there were 206 neor.le killed in Scotland and 92 in